Light

All light is produced by excited atoms

Excited Atoms Electrons in an energy level have a specific amount of energy If an electron absorbs energy, it is bumped into a higher energy level This produces an unstable or excited atom

Photons Atoms do not like to be excited. The electron will loose the extra energy by giving off a photon, allowing it to fall back into its original energy level Light is produced Photon – a packet of energy released by an excited electron

Electromagnetic Spectrum An arrangement of all electromagnetic waves by decreasing wavelength and therefore increasing frequency

Longest wavelength ROY – G – BIV shortest wavelength Red Orange Yellow Green Blue Indigo Violet

Behavior of Light Light behaves like a wave The wave theory of light explains most of the properties and behavior of light very well. However, it can no longer explain all the things we’ve observed about light. Light behaves like a particle High energy light will produce an electric current when it strikes a metal plate, while low energy will not. If light was a continuous wave, even the energy from the lowly “red” light would eventually be absorbed and cause some electron movement – this does not happen.

Light Strikes Matter…. 3 Things Can Happen: 1.Light can be transmitted 2.Light can be absorbed 3.Light can be reflected

Light Can Be Transmitted Light passes through the substance it strikes Transparent – light passes through so you can see clearly – like window Translucent – Light passes through but it is scattered so you cannot see clearly – like wax paper Opaque – Light does not pass through – like construction paper

Light Can Be Absorbed Light passes through a substance and stays there Example: When light hits a red stop sign, the stop sign reflects mostly red wavelengths and absorbs all other colors so we do not see them

Light Can Be Reflected Light strikes a substance and bounces back Example: When light hits a red stop sign, the stop sign reflects mostly red wavelengths and absorbs all other colors so we do not see them

Reflection Reflection –bouncing back of a wave when it hits a surface it can’t pass through –Regular Reflection – very little scattering; the image looks exactly like the object –Diffuse Reflection – light is scattered in many different directions; if image is formed at all, it does not look like the object

Mirrors Mirrors REFLECT light Types of mirrors »Plane – a flat surface »Concave – surface of mirror curves inward »Convex – surface of the mirror caves outward

Refraction Refraction – the bending of waves as they enter a different medium Some mediums cause light to bend more than others Prism – an object that forms a spectrum as light passes through it

Lenses Lenses REFRACT light Types of lenses »Concave – thicker at the edges than at the center »Convex – thicker at the center than at the edges

Optics Optics is the science of controlling light Light can be controlled in 3 ways: 1. Block it 2. Reflect it 3. Bend it ( Mediums, mirrors, and lenses are used in optics)